With a navigating tanker, various forces act on the hull. For example, the hull itself is subjected to a longitudinal bending moment and torsional forces, the outer bottom plating and the outer side plating to the pressure of water, and the inner bottom plating and side wall of the hold (oil tank) to the load of oil cargo under gravity. To withstand these forces, the hull includes a large number of structural members such as longitudinal members (side longitudinal members, bottom longitudinal members, central girder, etc.) extending longitudinally of the ship and reinforcing traverse members (side reinforcing transverse members, bottom reinforcing transverse members, etc.) provided transversely of the ship. In the case of such a structure, however, longitudinal members and reinforcing transverse members are provided in an intersecting arrangement so that difficulties are encountered in building the hull by automatic work procedures (e.g. automatic welding). To assure automatic work procedures, therefore, we have conceived of a double shell structure which comprises longitudinal members only and includes no reinforcing transverse members. Nevertheless, use of the double shell structure for the hull involves various problems. For example, when the double shell structure is used only for the bottom of a ship of conventional construction, an external force acting on the outer side plating is transmitted to the bottom portion through reinforcing transverse members provided inside the outer side plating, but the inner and outer bottom platings will buckle because the bottom portion has no reinforcing transverse member. Conversely if the double shell structure is used for the side portion only, an external force acting on the bottom and delivered to the side portion through bottom reinforcing transverse members will buckle the inner and outer side platings because the side portion has no vertical reinforcing transverse member.
An object of the present invention is to provide a transverseless ship which has a double shell structure comprising an inner hull plating and an outer hull plating connected thereto by longitudinal members only and which is nevertheless free of the problem of buckling of the inner and outer platings, the double shell structure having an interior space which is advantageously used owing to the absence of reinforcing transverse members.
To fulfill the above object, the present invention provides a transverseless ship comprising at least opposite side portions and a bottom portion each having a double shell structure, the double shell structure comprising an inner hull plating and an outer hull plating connected together only by a plurality of connecting longitudinal members fixed to transverse bulkheads spaced apart longitudinally of the ship except by the transverse bulkheads, the bottom portion having a spaced defined by at least two optionally selected connecting longitudinal members and divided by a partition into an upper chamber and a lower chamber, the upper chamber being adapted in its entirety to pass a fluid therethough.
With the structure described, an external force acting on the hull can be transmitted through the connecting longitudinal members to the transverse bulkheads having sufficient strength to thereby prevent the inner and outer platings from buckling. Since at least one of the spaces defined by the connecting longitudinal members is utilized as a fluid channel, there is no need to provide additional fluid transport piping.
Further because the double shell structure has an inner hull plating and an outer hull plating which are connected together substantially by connecting longitudinal members only, the transverseless ship has the following advantages.
(1) Absence of reinforcing transverse members decreases the number of components, while absence of intersections between the connecting longitudinal members with reinforcing transverse members makes it possible to build the hull by automatic work procedures (e.g. automatic welding) with a greatly improved efficiency, further facilitating perfect inspection of the space defined by the inner and outer hull platings. PA1 (2) Because the connecting longitudinal members have no intersections with reinforcing transverse members, cracking is avoidable that would otherwise result from stress concentration at such intersections. PA1 (3) Spaces defined by the inner and outer hull platings and divided by the connecting longitudinal members only can be utilized as ballast tanks. Moreover, the ballast tank, which is not divided by reinforcing transverse members longitudinally of the ship drains completely with ease. PA1 (4) Even if a flammable liquid or gas should ingress into a space between the inner and outer hull platings owing to damage to the inner plating, the liquid or gas can be easily drawn off from the space to eliminate an explosion hazard since there is no transverse member dividing the space longitudinally of the ship. PA1 (5) Absence of reinforcing transverse members facilitates stress analysis for the hull and assures a rational arrangement of components for a weight reduction. PA1 (6) The double shell structure prevents outflow of cargo oil in the event of a collision with other ship or stranding. PA1 (7) Since the hold has no inside projections such as stiffeners, the inside wall of the hold can be coated, washed or stripped efficiently and properly and is smaller in the surface area to be coated.
Various features and advantages of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings.